Session VIII - Pelvis

Fri., 10/21/05 Pelvis, Paper #31, 3:24 pm

S2 Iliosacral Screw Fixation for Disruptions of the Posterior Pelvic Ring

Berton R. Moed, MD (n); Benjamin L. Geer, BA (n);
St. Louis University School of Medicine, St. Louis, Missouri, USA;
Wayne State University Medical School, Detroit, Michigan, USA

Purpose: Inserting iliosacral lag screws into the first sacral (S1) body has been well described. However, adequate space for the insertion of 2 screws into the S1 body is often a concern. Due to its relatively small size and, therefore, increased risk for any screw misdirection resulting in nerve root injury or spinal canal compromise, the second sacral (S2) body has not been viewed as a viable alternative iliosacral location. In a CT study in 30 human volunteers, Carlson et al defined the surgical anatomy of the S2 vestibule and indicated that safe use of an iliosacral S2 screw was possible. However, no body of clinical data exists. The purpose of this study was to evaluate the clinical safety and efficacy of the iliosacral S2 screw for pelvic fracture fixation.

Methods: Between 1996 and 2001, 49 patients were treated with S2 iliosacral screws. There were 9 bilateral injuries with a total of 53 S2 screws inserted. Patients ranged in age from 14 to 71 years. Follow-up averaged 19 months. Pre- and postoperative radiographic evaluation included AP, inlet and outlet pelvic radiographs, and a 2-dimensional CT with 3-mm slice thickness. Candidates for S2 screw fixation required adequate space on CT, which was defined as a minimum of 1 cm between foramina on 3 sequential preoperative CT slices in conjunction with inadequate S1 available space. Intraoperative stimulus-evoked electromyographic monitoring was used routinely.

Results: There were no intraoperative iatrogenic nerve injuries. Satisfactory screw position was documented on the postoperative CT in all cases. However, early postoperative loss of reduction requiring revision surgery occurred in two older osteopenic patients. One was associated with injury to the S1 nerve root, which had full return of function within 1 year.

Conclusions/Significance: Contrary to supposition, S2 iliosacral screw fixation is a safe and effective technique that should be added to our surgical armamentarium. However, it should be used with caution in patients with pelvic osteopenia.

If noted, the author indicates something of value received. The codes are identified as a-research or institutional support; b-miscellaneous funding; c-royalties; d-stock options; e-consultant or employee; n-no conflicts disclosed, and *disclosure not available at time of printing.